Women who are past the menopause gain 0.7 kg weight every year. And their waist measurement increases by 0.7 cm each year too. [Am J Epidemiol. 2004 Nov 1;160(9):912-22.] Not exactly an encouraging prospect, but according to researchers at the University of Arizona it's possible to do something about this. Women who start strength training can slow down the growth of their spare tyre.

Study

The researchers studied 122 women aged between 40 and 65 over a period of six years. The researchers divided the women into three groups. The first of these was the control group, consisting of women who did no training or any other form of sport. [Control]

The second group of women trained three times a week. [Exercise] The women trained in such a way that they had at least one rest day between training sessions. Each workout lasted a good hour and consisted of a 10-minute warming up, 25 minutes of intensive cardio training, half an hour of strength training, five minutes core training and ended with some stretches.

The third group consisted of women who in the first of the six years that the trial lasted were not active, but then did do exercise for the remaining five years. [Cross over]

Results
The figure below shows that the control group built up almost two kg of fat, while the Exercisers only accumulated 300 g fat.

The researchers then looked at the level of intensity at which the women trained. They measured this by determining the number of all the kilograms that the women had squatted during the trial.

The researchers then used this data to divide the women in the Cross-over and Exercise groups into three tertiles: three equal-sized groups, of which tertile 1 was the women with the lowest amount of kgs and tertile 3 the women with the largest amount of kgs.

The figure below shows that the more intensively the women had trained, the greater the slimming effect of strength training.

Part of the slimming effect of strength training is of course due to the couple of hundred kilocalories you burn during each workout. But another part of the effect is due to the muscle mass that is built up. Each kg of muscle mass that you gain boosts your energy burning, and the most conservative estimates put that at 20 kilocalories per day. And on top of that there's also the EPOC effect.

Conclusion
"In spite of the limitations inherent in a long-term study, results were significant and this study is one of the first to show the association of resistance training and prevention of weight gain", the researchers summarise.

"In light of the positive effects of resistance training on bone mass density, muscle function and lean mass, and its potential for contributing to the prevention of osteoporosis and debilitating fractures, resistance training for weight loss and maintenance is particularly attractive for overall chronic disease prevention in postmenopausal women."